In order to simplify the production of lymphokine-activated killer (LAK) cells for therapeutic use, an automated cell separator (CS-3000, Fenwal) was adapted to: (1) process large volumes of whole blood for collection of leukocyte concentrates from cancer patients, (2) purify the lymphocyte fraction by automated Ficoll-Hypaque density gradient sedimentation, (3) culture the lymphocytes in platelet storage bags, and (4) harvest and concentrate the LAK cells out of culture. Nearly 100 LAK cell preparations have been processed in this manner. Automated density gradient sedimentation resulted in high lymphocyte recovery rates with significantly less platelet contamination than could be achieved using standard manual methods. In addition, automated processing was performed in a closed-system disposable apheresis kit, reducing the potential for bacterial contamination of the cell product. Culture of the lymphocytes in flexible plastic bags resulted in reductions in incubator space and culture media, and improved ease of handling of the cells. Lastly, automated harvest of cells out of culture led to increases in cell recovery without any damage to cell viability. Use of standard blood bank and apheresis technology in the collection, processing, culture, and harvest of LAK cells can significantly increase the efficiency and reduce the complexity of LAK generation and safeguard the sterility of the final product. Adoption of these techniques by smaller medical centers should allow LAK therapy to find more widespread use in the treatment of cancer. This work was done in collaboration with the Surgery Branch, NCI, as an addendum to Protocol No. 86-C-50.